diff options
| -rw-r--r-- | gcc/ada/ChangeLog | 5 | ||||
| -rw-r--r-- | gcc/ada/urealp.adb | 63 |
2 files changed, 46 insertions, 22 deletions
diff --git a/gcc/ada/ChangeLog b/gcc/ada/ChangeLog index aa81ae6..e42cd8e 100644 --- a/gcc/ada/ChangeLog +++ b/gcc/ada/ChangeLog @@ -1,3 +1,8 @@ +2011-08-04 Geert Bosch <bosch@adacore.com> + + * urealp.adb (Equivalent_Decimal_Exponent): Avoid the use of floating + point. + 2011-08-04 Emmanuel Briot <briot@adacore.com> * makeutl.adb (Compute_Builder_Switches): no longer accept a unit name diff --git a/gcc/ada/urealp.adb b/gcc/ada/urealp.adb index e28ee59..e11235f 100644 --- a/gcc/ada/urealp.adb +++ b/gcc/ada/urealp.adb @@ -6,7 +6,7 @@ -- -- -- B o d y -- -- -- --- Copyright (C) 1992-2010, Free Software Foundation, Inc. -- +-- Copyright (C) 1992-2011, Free Software Foundation, Inc. -- -- -- -- GNAT is free software; you can redistribute it and/or modify it under -- -- terms of the GNU General Public License as published by the Free Soft- -- @@ -128,7 +128,7 @@ package body Urealp is -- U is a Ureal entry for which the base value is non-zero, the value -- returned is the equivalent decimal exponent value, i.e. the value of -- Den, adjusted as though the base were base 10. The value is rounded - -- to the nearest integer, and so can be one off. + -- toward zero (truncated), and so its value can be off by one. function Is_Integer (Num, Den : Uint) return Boolean; -- Return true if the real quotient of Num / Den is an integer value @@ -244,29 +244,48 @@ package body Urealp is function Equivalent_Decimal_Exponent (U : Ureal_Entry) return Int is - -- The following table is a table of logs to the base 10 - - Logs : constant array (Nat range 1 .. 16) of Long_Float := ( - 1 => 0.000000000000000, - 2 => 0.301029995663981, - 3 => 0.477121254719662, - 4 => 0.602059991327962, - 5 => 0.698970004336019, - 6 => 0.778151250383644, - 7 => 0.845098040014257, - 8 => 0.903089986991944, - 9 => 0.954242509439325, - 10 => 1.000000000000000, - 11 => 1.041392685158230, - 12 => 1.079181246047620, - 13 => 1.113943352306840, - 14 => 1.146128035678240, - 15 => 1.176091259055680, - 16 => 1.204119982655920); + type Ratio is record + Num : Nat; + Den : Nat; + end record; + + -- The following table is a table of logs to the base 10. All values + -- have at least 15 digits of precision, and do not exceed the true + -- value. To avoid the use of floating point, and as a result potential + -- target dependency, each entry is represented as a fraction of two + -- integers. + + Logs : constant array (Nat range 1 .. 16) of Ratio := + (1 => (Num => 0, Den => 1), -- 0 + 2 => (Num => 15_392_313, Den => 51_132_157), -- 0.301029995663981 + 3 => (Num => 731_111_920, Den => 1532_339_867), -- 0.477121254719662 + 4 => (Num => 30_784_626, Den => 51_132_157), -- 0.602059991327962 + 5 => (Num => 111_488_153, Den => 159_503_487), -- 0.698970004336018 + 6 => (Num => 84_253_929, Den => 108_274_489), -- 0.778151250383643 + 7 => (Num => 35_275_468, Den => 41_741_273), -- 0.845098040014256 + 8 => (Num => 46_176_939, Den => 51_132_157), -- 0.903089986991943 + 9 => (Num => 417_620_173, Den => 437_645_744), -- 0.954242509439324 + 10 => (Num => 1, Den => 1), -- 1.000000000000000 + 11 => (Num => 136_507_510, Den => 131_081_687), -- 1.041392685158225 + 12 => (Num => 26_797_783, Den => 24_831_587), -- 1.079181246047624 + 13 => (Num => 73_333_297, Den => 65_832_160), -- 1.113943352306836 + 14 => (Num => 102_941_258, Den => 89_816_543), -- 1.146128035678238 + 15 => (Num => 53_385_559, Den => 45_392_361), -- 1.176091259055681 + 16 => (Num => 78_897_839, Den => 65_523_237)); -- 1.204119982655924 + + function Scale (X : Int; R : Ratio) return Int; + -- Compute the value of X scaled by R + + function Scale (X : Int; R : Ratio) return Int is + type Wide_Int is range -2**63 .. 2**63 - 1; + + begin + return Int (Wide_Int (X) * Wide_Int (R.Num) / Wide_Int (R.Den)); + end Scale; begin pragma Assert (U.Rbase /= 0); - return Int (Long_Float (UI_To_Int (U.Den)) * Logs (U.Rbase)); + return Scale (UI_To_Int (U.Den), Logs (U.Rbase)); end Equivalent_Decimal_Exponent; ---------------- |